Gas drying system



Nov. 29, 1966 R. c. MOTT 3,

GAS DRYING SYSTEM Filed May 27, 1964 IN VENTOR. Paw/42.0 6? W077 47 TOPII EV United States Patent 3,287,883 GAS DRYING SYSTEM Richard C. Mott, Harwood Heights, Ill., assignor to Honeywell Inc., Minneapolis, Minn., a corporation of Delaware Filed May 27, 1964, Ser. No. 370,576 7 Claims. (Cl. 55-33) The present invention is directed generally to a system for drying air coming from an air compressor for storage when used with certain types of pneumatic control systems. More specifically, the present invention is directed to a single desiccant tank type of drying device which utilizes air flow to the atmosphere as the sole drying means [for the desiccant on the portion of the cycle when the desiccant is not used as a drying agent for air being stored in the compressor tank.

It has become well known that air compressed and stored in tanks for use in control systems, particularly temperature control systems, must be dried in order to obtain long and reliable operation of the systems. When moisture is contained in relatively large quantities in air being retained in pneumatic control systems, the systems eventually malfunction due to build ups of deposits from the moisture in the air, as well as, corrosion that results from the moisture. In the past, various systems have been employed which utilize desiccants, cooling media, and other means for absorbing the moisture from the air compressed for pneumatic control systems. As a general rule, the systems that utilize desiccants have required that the systems have two desiccant tanks. The first desiccant tank is used while the second desiccant tank is recharge-d. The recharging cycle almost invariably requires heat or the application of relatively dry air obtained from some secondary source. In certain types of air dryer systems the air for the secondary source is in fact the air stored in the compressor storage tank, but this system again requires that two separate desiccant tanks be supplied for proper operation. In order to overcome the disadvantages of the double desiccant system, or systems that utilize heating means for regen-' erating of a desiccant tank, the present invention has been developed.

The primary object of the present invention is to disclose a single tank type of desiccant dryer system for a compressor used in pneumatic and gas systems.

Another object of the present invention is to disclose a more economical dryer system that is adequate to supply air for most pneumatic control systems without the inherent extra cost of drying equipment.

Still a further object of the present invention is to disclose a method of operating a compressor with a desiccant tank type dryer where both the dry and renewal air are supplied by a single system. I

Yet a further object of the present invention is to disclose a compressor dryer system that utilizes a compressor operating substantially continuously to supply air both for a pneumatic control system and for drying the desiccant in the moisture removal portion of the system.

These and other objects will become apparent when the single drawing is fully considered along with the present disclosure.

In the single figure disclosed in connection with the present invention, there is pictorially presented an air compressor system 10 that includes a conventional airstorage tank 11 including a drain petcock 12 and an air outlet 13. The air outlet 13 is connected to a pressure regulating valve 14 and a pressure indicating gauge 15. The outlet of the pressure regulating valve 14 is supplied on a pipe 16 that in turn is used to supply compressed air to any type of pneumatic system, such as a temperature control system. The air being supplied on pipe 16 should be as dry as practical, and the object of the present invention is directed to a dryer system for use in supplying dry air at the pipe 16.

Mounted on top of the air tank 11 is a platform 20 including a projection 21 that supports the pressure regulator 14. The platform 20 has a conventional air compressor 22 mounted thereon. The air compressor 22 has a drive wheel 23 that is turned by a belt 24. The belt 24 is in turn rotated by a conventional electric motor 25. The motor 25 receives power \from cable 26 and the motor 25 is further mounted by base 27 on the platform 20. The power cable 26 is connected to a pressure operated time delay means 30 of a type that will be briefly described later in the present specification. The pressure operated time delay means 30 has an ofi-on switch 31 that supplied the input power from cable 32 for the over-all control of the compressor 10. The pressure operated time delay means 30 further has a pressure inlet means 33 connected to a pipe 34 that is joined into the air pressure section of the system, as will be subsequently described.

The compressor 22 has a conventional screened inlet 36 and an outlet 37. When the compressor 22 is operated by the motor 25, atmospheric pressure air is taken into the inlet 36, compressed by the compressor 22 and supplied at a pressure substantially above the atmospheric pressure at the outlet 37. The outlet 37 is connected by a pipe 38 to a desiccant tankhaving an inlet 39. The makeup of the desiccant tank will be described in some detail subsequently, but for the present can be considered as a conventional tank containing some form of desiccant material for drying the air supplied to inlet 39 from the compressor outlet 37. The desiccant tank 40 has an. outlet 41 which is connected by pipe 42 through a con-.

ventional trapbowl 43 [for removal of oil and foreign materials that might possibly pass through .the desiccant tank 40. The trap bowl 43 joins at a T 44 to a pipe 45 which in turn is connected through a conventional checkdump valve means has an outlet 51 to the atmosphere.

The outlet 51 could be supplied to any convenient drain or may be merely connected to the atmosphere, for a purpose to be noted subsequently. The dump valve means 50 further is connected by a pressure control line 52 to a control means 53 that is responsive to the pressure in tank 11 through the pipes 54 and 55, along with the safety valve 56. The safety valve 56 is placed between the air tank 11 and the control means 53 and provides a safety blowofi in case of an excess of pressure in tank '11. The excess air is bled to the atmosphere by pipe 57. The safety valve 56 may be of any conventional type and the only requisite in the present application is that it supply a passage which is open between the pipes 54 and 55 so' that the pressure operative control means 53 is responsive could bypass the safety valve 56 entirely, if desired.

3 Operation The easiest manner in which to consider the present invention is by describing the mode of operation of the equipment. Electric power is supplied by cable 32 and in turn is controlled by switch 31. When the tank 11 has little or no air therein, the pressure operated time delay means 30 acts as a direct connection between the switch 31 and the cable 26 so that electric power is supplied to motor 25. The motor 25 then is placed into operation driving the compressor 22 to draw air into the inlet 36 where it is compressed by the compressor and supplied at the compressor outlet 37. The air from the outlet 37 passes directly into the desiccant tank 40 wherethe air is dried before the air passes to the pipes 34- and 42. The pressure supplied to pipe 34 is fed back to the inlet 33 of the time delay means. For the present explanation, the pressure in pipe 34 is just building up and an electric circuit is maintained between the input electric cable 32 and the motor 25. As such, thecompressor 22 continues to run forcing air through the desiccant tank 40 and into the pipe 42. The pipe 42 leads the trap bowl 43 to the T-44 where air is then supplied through the check valve 46 into the air storage tank 11. The air passing through the just described circuit is dried by the desiccant tank 40 to a suificient degree so that the air supplied on pipe 16 from the outlet of the air storage tank is sufiiciently dry to be used in pneumatic systems.

As the compressor 22 continues to operate, the level of the pressure in tank 11 continues to increase. The

pressure in tank 11 is supplied by pipes 54 and 55 to the pressure control means 53 which in turn controls via pipe 52 the dump valve means 50. Upon reaching a set limit of pressure in tank 11, the pressure control means 53 supplies pressure on pipe 52 to the dump valve 50 opening the dump valve 50 to the atmosphere through pipe 51. The opening of the dump valve 50 removes the pressure from the T 44. Since the storage tank 11 is supplied with air through check valve 46, the opening of the dump valve 50 does not effect the pressure stored in tank 11. The sudden dropping of the pressure in the T 44 by the operation of the dump valve 50 to the atmosphere via pipe 51, supplies a substantially atmospheric pressure in the pipe 42 at the outlet 41 of the desiccant tank 40. The compressor 22 continues to run supplying compressed air from the inlet'36 to the outlet 37 and passing'it into the desiccant tank 40. With the dump valve 50 open, the air passage is substantially to the atmospheric pressure thereby allowing a large, low pressure flow of air through the desiccant tank 40. This flowof air carries oif the excess moisture that has been collecting in the desiccant tank '40 thereby tending to dry the desiccant material. The compressor 22 con tinues to run for a fixed period of time that is determined by the time delay means 30 which has been activated by the reduction of pressure in pipe 34 to the atmospheric level. As soon as a fixed time delay occurs, the time delay means 30 turns off the compressor motor 25 stopping the compressor. If, during the period of time when the drying cycle is in operation wherein the air passes through theldesiccant tank 40 to the atmosphere via pipe 51, the pressure in tank 11 drops due to the usage of air on the pipe 16, the control means 53 operates by means of the pipe 52 'to close the dump valve 50. The closing of the dump valve 50 allows the compressor 22 to force air through the desiccant tank 40 at a higher back pressure thereby drying the air once again before it passes into the storage tank 11 through the check valve i 40 is dried by a large, low pressure flow of air to the atmosphere. The present system also incorporates 'a' time delay means 30 so that the compressor will be shut off after running for a specified time in its drying condition for the desiccant tank 40.

It should be noted that the function of time delay means 30 can be eliminated completely and the system be left to operate with the motor 25 energized continu ously thereby driving the compressor 22 continuously. In this mode of operation the compressor 22 would alternately supply air from the inlet 36 to the outlet 37 through the desiccant tank 40 to the atmosphere or to the air storage tank 11 depending on the state of the pressure in the storage tank 11. If the compressor 22 is left to run continuously, the dump valve 50 is left open by the operation of the control means 53.and the desiccant tank 40 is dried substantially continuously. The savings in the removal of the time delay means 30 and running the motor 25' and compressor 22 continuously is a matter of economics that is bestdecided upon de-' pending on the specific application of the present invention. Either mode of operation is both practical and feasible.

It will be noted that the present invention entails two specific modes of methods of operation. The first is the drying of compressed air by forcing the compressed air through a desiccant tank where the back pressure is substantial and thereby allowing the desiccant to remove a high level of moisture from the The second step of the method of operation is to open the outlet of the' desiccant tank to the atmosphere thereby allowing the air to pass through the desiccant tank in a manner that is substantially free and at atmospheric pressure. This allows the air to pass through the desiccant tank in a manner that-tends to reduce the moisture content of the desiccant tank so that it is regenerated. Extensive tests have been run on this type of system and it has been shown that the dewpoint of the air contained in the storage tank 11 can be sufiiciently lowered by operating the desiccant first at a high back pressure to remove moisture and then at a low back pressure to dry the desiccant within the requirements of most normal pneumatic control systems. The extensive tests on this type of a system have further shown that the type of desiccant contained in the desiccant tank 40 can be varied extensively and still be practical. The desiccant tank means 40 can contain a conventional desiccant material such as silica gel, or it can contain any type of material having a large surface area. Specific tests have been run which have used coarse gravel for the desiccant material. The coarse gravel, having a large surface area, can be used with success in the present type of operation. Other types of desiccant materials such as wood blocks or granules along with other types of desiccant materials are practical in this type of an'operation and the method of operating the device has been proven satisfactory in extensive testing procedures. It is thus apparent that the type of desiccant material used can be varied exten-.

sively in the present invention and that no specific limitation' need be drawn to the type of desiccant or the construction of the desiccant tank.

In the present application a pressure operated dun-11p valve has been disclosed at 50 operated by a control means 53 through the connectinigpipe 52. It is apparent that a pressure to electric type of switch could replace the pressure operated switch 53 and that the connection between the pressure operated switch 53 and the dump valve 50 could lbe an electrical connection. In that case, the dump valve means 50 could be such as a solenoid valve operated electrically rather than the pressureoperated' valve specifically shown in the single drawing contained with this. application. The type of pressure sensing con-' trol switch and the type of dump valve rform no part of the present invention and can abe anywt-ype that would perform the function specifically: set forth. 1

It becomes obvious from considering the method of operation, and the fact that various types of components could be readily placed in the system depending on the skill of the persons in the art, that the applicant wishes to be limited in the scope of his invention only by the scope of the appended claims and not by the specific disclosure contained herein.

I claim:

1. A compressor unit for supplying dry air to pneumatic systems, including: a controlalble air compressor operatively driven to compress air taken in at an atmospheric pressure and delivered to an outlet at a higher than atmospheric pressure; a single desiccant tank containing a desiccant material having a relatively large surface area connected to said outlet to receive said compressor air; said desiccant tank having an outlet connected through a check valve to an air storage tank for said pneumatic system; said desiccant tank outlet further connected to a pressure operated dump valve which is in turn connected to the atmosphere; said compressor air being dried by said desiccant material as said air passes into said air storage tank through said check valve when said dump valve is closed; control means responsive to the air pressure in said air storage tank and connected to said pressure operated dump valve to control said dump valve; said desiccant material being dried by said compressor air when said controlmeans opens said dump valve to the atmosphere thereby supplying a low pressure outlet for said compressor air as it passes through said desiccant material; and pressure operated time delay means connected to said desiccant tank outlet; said time delay means further being connected to said air compressor t-o operatively control said compressor in response to the pressure in said desiccant tank outlet; said time delay means stopping said compressor when said pressure in said desiccant tank outlet has been at substantially atmospheric pressure tor a fixed time.

2. A compressor unit for supplying dry air to pneumatic systems, including: air compressor means operatively driven to compress air taken in at an atmospheric pressure and delivered to an outlet at a higher than atmospheric pressure; desiccant tank means including desiccant means connected to said outlet to receive said compressor air; said desiccant tank means having an outlet connected through check valve means to an air storage tank for said pneumatic system; said desiccant tank means outlet further connected to dump valve means which is in turn connected to the atmosphere; said compressor air being dried by said desiccant means as said air passes into said air storage tank through said check valve means when said dump valve means is closed; control means responsive to the air pressure in said air storage tank and connected to control said dump valve means; said desiccant means being dried by said compressor air when said control means opens said dump valve-means to the atmosphere thereby supplying a low pressure outlet for said compressor air as it passes through said desiccant means; and pressure operated time delay means connected to said desiccant tank outlet; said time delay means further being connected to said air compressor means to operatively control said compressor means in response to the pressure in said desiccant tank outlet; said time delay means stopping said compressor means when said pressure in said desiccant tank outlet has been at substantially atmospheric pressure for a fixed time.

3. A compressor unit for sup-plying dry air to pneumatic systems, including: air compressor means operatively driven to compress air taken in at an atmospheric pressure and delivered to an outlet at a higher than atmospheric pressure; desiccant tank means including desiccant means connected to said outlet to receive said compressor air so that said compressor lair always passes through said desiccant tank means in one direction; said desiccant tank means having an outlet connected through check valve means to an air storage tank for said pneumatic system; said desiccant tank means outlet further connected to dump valve means which is in turn connected to the atmosphere; and control means responsive to the air pressure in said air storage tank and connected to control said dump valve means; said compressor air being dried by said desiccant means as said air passes into said air storage tank through said check valve means when said dump valve means is closed; said desiccant means being dried by said compressor air when said control means opens said dump valve means to the atmosphere thereby supplying a low pressure outlet for said compressor air as it passes through said desiccant means in said one direction.

4. A method of removing a portion of the moisture from air for pneumatic powered systems, including: passing compressed air in a single direction through a tank containing a desiccant into an air storage tank at a pressure above atmospheric pressure thereby all-owing the desiccant to remove moisture from the air; and then diverting the corn-pressed air in said single direction to the atmosphere through the tank containing the desiccant at a pressure of substantially that of the atmosphere thereby allowing the desiccant to be dried of moisture received from the air compressed at the higher pressure when the air passed into the air storage tank.

5. A method of removing a portion of the moisture from air for pneumatic powered system, including: pass ing compressed air in a single direction through a tank containing a desiccant having a relatively large surface area into an air storage tank at a pressure above atmospheric pressure thereby allowing the desiccant to remove moisture from the air; then diverting the compressed air in said single direction to the atmosphere through the tank containing the desiccant at a pressure of substantially that of the atmosphere thereby allowing the desiccant to be dried of the moisture received from the air compressed at the higher pressure when the air passed into the air storage tank; and returning the compressed air flow in said single direction through the desiccant tank into the air storage tank upon the pressure in the air storage tank dropping to a predetermined pressure.

6. A compressor unit for supplying dry air to pneumatic systems, including: air compressor means operatively driven to compress air taken in at an atmospheric pressure and delivered to an outlet at a higher than atmos pheric pressure; desiccant tank means including desiccant means connected to said outlet to receive said compressor air; said desiccant tank means connected through check valve means to an air storage tank for said pneumatic system to provide a unidirectional flow of air through said desiccant tank means; said desiccant tank means further connected to dump valve means which is in turn connected to the atmosphere; and control means responsive to the air pressure in said air storage tank and connected to control said dump valve means; said compressor air being dried by said desiccant means as said unidirectional air flow passes into said air storage tank through said'check valve means when said dump valve means is close-d; said desiccant means being dried by said unidirectional compressor air flow when said control means opens said dump valve means to the atmosphere thereby supplying a low pressure outlet for said compressor air as it passes through said desiccant means in said single direction.

7. A compressor unit for supplying dry gas to a system, including: gas compressor means operatively driven to compress gas taken in at a first pressure and delivered to an outlet at a higher than said first pressure, desiccant tank means including desiccant means connected to said outlet to receive said compressed gas; said desiccant tank means connected through check valve means to a gas storage tank for said system to provide a unidirectional flow of gas through said desiccant tank means; said desiccant tank means further connected to dump valve means which is in turn connected to the first pressure;

3,287,883 7 8 and control means responsive to the gas pressure in said References 'Cited by the Examiner gas storage tank and connected'to control said du-rmp valve UNITED STATES PATENTS means; said compressed :gas being dried by said desiccant means as said unidirectional gas flow passes into said 2,322,603 6/1943 Thumun gas storage tank through said check valve means when 5 2,580,404 1/ 1952 Bush said dump valve means is closed; said desiccant means 2,534,8 2/ 95 L I-0011f 5558 being dried by said unidirectional compressed gas flow 2,955,673 10/1960 Kennedy 55-33 when said control means opens said dump valve means 3,147,095 9/1964 K-anuch 5533 to the first pressure thereby supplying a low pressure 3,225,517 12/1965 Wachsmuth 5533 outlet for said compressed gas as it passes through said 10 V desiccant means in said single direction. LAURENCE V. EFNER, Primary Examiner. 

1. A COMPRESSOR UNIT FOR SUPPLYING DRY AIR TO PNEUMATIC SYSTEMS, INCLUDING: A CONTROLABLE AIR COMPRESSOR OPERATIVELY DRIVEN TO COMPRESS AIR TAKEN IN AT AN ATMOSPHERIC PRESSURE AND DELIVERED TO AN OUTLET AT A HIGHER THAN ATMOSPHERIC PRESSURE; A SINGLE DESICCANT TANK CONTAINING A DESICCANT MATERIAL HAVING A RELATIVELY LARGE SURFACE AREA CONNECTED TO SAID OUTLET TO RECEIVE SAID COMPRESSOR AIR; SAID DESICCANT TANK HAVING AN OUTLET CONNECTED THROUGH A CHECK VALVE TO AN AIR STORAGE TANK FOR SAID PNEUMATIC SYSTEM; SAID DESICCANT TANK OUTLET FURTHER CONNECTED TO A PRESSURE OPERATED DUMP VALVE WHICH IS IN TURN CONNECTED TO THE ATMOSPHERE; SAID COMPRESSOR AIR BEING DRIED BY SAID DESICCANT MATERIAL AS SAID AIR PASSES INTO SAID AIR STORAGE TANK THROUGH SAID CHECK VALVE WHEN SAID DUMP VALVE IS CLOSED; CONROL MEANS RESPONSIVE TO THE AIR PRESSURE IN SAID AIR STORAGE TANK AND CONNECTED TO SAID PRESSURE OPERATED DUMP VALVE TO CONTROL SAID DUMP VALVE; SAID DESICCANT MATERIAL BEING DRIED BY SAID COMPRESSOR AIR WHEN SAID CONTROL MEANS OPENS SAID DUMP VALVE TO THE ATMOSPHERE THEREBY SUPPLYING A LOW PRESSURE OUTLET FOR SAID COMPRESSOR AIR AS IT PASSES THROUGH SAID DESICCANT MATERIAL; AND PRESSURE OPERATED TIME DELAY MEANS CONNECTED TO SAID DESICCANT TANK OUTLET; SAID TIME DELAY MEANS FURTHER BEING CONNECTED TO SAID AIR COMPRESSOR TO OPERATIVELY CONTROL SAID COMPRESSOR IN RESPONSE TO THE PRESSURE IN SAID DESICCANT TANK OUTLET; SAID TIME DELAY MEANS STOPPING SAID COMPRESSOR WHEN SAID PRESSURE IN SAID DESICCANT TANK OUTLET HAS BEEN AT SUBSTANTIALLY ATMOSPHERIC PRESSURE FOR A FIXED TIME. 